JPS58174295A - Used of polyitaconic acid as critical scale inhibitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the use of polyitaconic acid as a critical scale inhibitor.

Aqueous systems having dissolved inorganic salts are commonly used in operations involving heat transfer, such as heating, cooling, and evaporative distillation.

These salts often become insoluble during these operations and are deposited as scale on heat transfer surfaces, resulting in reduced heat transfer and eventual failure of the device. In general, inorganic salts of scale include alkali metals such as calcium, magnesium, iron and lead, and other metal cations and bicarbonates.

Resulting from anions such as carbonate, hydroxide, sulfate and phosphate. Many factors influence scale formation, including the pH of the water, the nature of the dissolved salts, and the operating temperature.

Many additives have been proposed as inhibitors of mineral scale formation. Of particular interest are additives known as critical scale inhibitors that inhibit scale at very low additive concentrations of 1 ppm or less. Inhibitors include acrylic acid and methacrylic acid homopolymers and copolymers with acids such as maleic anhydride and fumaric acid.These additives have proven effective at critical concentrations, but are easily and There is still a need for other effective critical scale inhibitors that can be produced inexpensively. It is therefore a primary object of the present invention to provide such other critical scale inhibitors. .

Polyitakynic acids of various molecular weights have shown many uses.

For example, U.S. Patent No. 3,005,873
Discloses its use as a cleaning aid in papermaking and as an anti-flocculant for papermaking. US Pat. No. 6,608,067 suggests use as a detergent virgoo, while US Pat. No. 3,405,060 discloses use as a sequestering agent.

and British Patent Publication CB 2054 E', 48
A indicates that the above polyitaconic acid is suitable for removing scale from boilers. However, polyitaconic acid as a critical scale inhibitor is not disclosed or suggested.

It has now been discovered that low molecular weight polyitaconic acids are particularly effective as critical scale inhibitors.

Therefore, the present invention provides a method for preventing scale formation in water containing scale-forming impurities, such as seawater for desalination, which comprises combining the water with polyitaconic acid having a weight average molecular weight of about 500 to 2000, or its alkali metal, ammonium or amine. A process comprising incorporating a critical scale inhibitor consisting of a salt, preferably at a concentration of about 0.5 to 10 ppm.

The above polyitacon 5I4 is preferably about 500 to 100
It has a weight average molecular weight of 0. The above method also preferably comprises adding sulfuric acid to the seawater in an amount to neutralize about 55-85% of the bicarbonate alkalinity of the seawater.

The critical scale prevention method of the present invention demonstrates the use of controlled low molecular weight polyitaconic acids, the weight average molecular weight of the polymer being between about 500 and 2000, preferably between about 500 and 1000.

I don't want to be taken by conventional wisdom, but since high molecular weight polyitaconic acid precipitates from seawater as a sodium complex, polymers in the low molecular weight range mentioned above are more effective as critical scale inhibitors, especially for seawater desalination. Therefore, the effective amount is small.

Such polyitaconic acids can be prepared, for example, by solution polymerization in a ketonic solvent such as methyl isobutyl ketone at a moderate reaction temperature of about 90-150C. The reflux temperature of the solvent is commonly used. The polymerization is carried out using a relatively high concentration (0,1
0 to 0.20 mol (monomer)). Such initiators are di-t-butyl peroxide, dicumyl peroxide, di-t-butyl diperoxyphthalate and t-butyl peroxymaleate. Such polymerizations usually provide relatively good yields of the desired polymer C in relatively short reaction times (about 0.5 to 8 hours).

Product polymers having a needle weight of about 500 to 2000 can be isolated from the final polymerization solution by standard isolation techniques, -/J. When used in an aqueous system, the solvent in the final polymerization solution is removed (e.g. by azeotropy) from the solution and replaced with water, and the resulting aqueous solution is used to directly isolate the polymer. Use after diluting or concentrating with Shisho-e. This solution can also be neutralized to form an aqueous solution of a combined alkali metal, ammonium or amine salt. Suitable alkali metal bases for neutralization are sodium hydroxide, potassium hydroxide and lithium hydroxide, while suitable ammonium and amine bases include ammonia, ammonium hydroxide, mono-, di- and trialkyl amines (carbon 1 to 5), pyridine, morpholine and lutidine.

The itaconic acid homopolymers of the present invention have general applicability as critical scale inhibitors, but are particularly useful in preventing alkaline calcium and magnesium scale formation in methods such as evaporative desalination of seawater. This polymer is added to the water to be treated in an effective amount, usually about 0.1 to 100 ppm, preferably about 0.5 to 10 ppm, to inhibit scale formation. Such additions are diluted to a concentration of about 1-60% by weight.

Other additives commonly used in combination with critical scale inhibitors are also effective with the novel inhibitors of this invention. Particularly useful are mineral acids, especially sulfuric acid, which neutralize some of the alkalinity due to bicarbonates present in the seawater etc. to be desalted. The degree of bicarbonate neutralization is usually about 60-80%, especially about 55-85%. Foam control agents, corrosion inhibitors and oxygen scavengers may also be utilized with these new scale inhibitors.

The following examples are merely illustrative and serve to limit the invention.

Example 1 Production of low molecular weight polyitaconic acid Six-necked 50 with overhead stirrer, reflux condenser, thermometer and nitrogen inlet
150 in a 0#ll round bottom flask? Methyl isobutyl ketone, 130. I P (1,0 mol) of itaconic acid, and 14.65i' (0,1-r-l) of di-t-
Butyl peroxide was added. The flask was purged with nitrogen and heated to reflux ( 117C) under a nitrogen atmosphere.

After refluxing for 40 minutes, 150 mJ of water was added to the reaction solution and the methyl isobutyl keto/solvent was removed by azeotropic distillation. When the resulting aqueous solution was cooled to 25C, unreacted itaconic acid crystallized. The slurry was filtered to yield 81.3 F unreacted itaconic acid solids and 235.8 with a solids content of 20.1 x weight %! The amber p liquid of i' was collected. This shows that polyitaconic acid was obtained in a yield of 36.5% based on the monomers used; this homopolymer was analyzed by size exclusion high performance liquid chromatography and had a weight average molecular weight of 800. I understand.

Example 2 Evaluation as a critical scale inhibitor Laboratory experiment using synthetic seawater in which the polyitaconic acid of the above example (Mw 800) was prepared by solution polymerization in water at 92C with a sodium persulfate initiator and a polyitaconic acid with a weight average molecular weight of 7000. The scale inhibition ability was determined by testing in a single-stage flash evaporator. Laboratory Evaporator Operation and Testing Methods by Auerb
Desal by ach and Carruthers
inatxon, 31 m279 (1979). The synthetic seawater was 1 Standard Synthetic Seawater Composition 1 with increasing bicarbonate content by 9 increments of 0.25 y/- from The Office of Sarin Water. The polymer concentration used in the test was 3 ppm based on active solids.
Met.

The results of the test are as follows.

The % precipitated scale is determined by the following formula: Polymers exhibiting a low %1 precipitated scale at a given usage rate indicate superior performance.

Polyitaconic acid Mw=800 12.8 Polyitaconic acid Mw=7000 19.7 Control (without additives) 36° Patent applicant
Pfizer Inc. (4 others)

Claims (1)

[Scope of Claims] (1) A method for preventing scale formation in water containing scale-forming impurities, comprising:
00-2000 polyitaconic acid or its alkali metal, ammonium or amine salts. (2) The average molecular weight of polyitaconic acid is approximately 500.
10. The method of claim 1, wherein: (3) The method according to claim 1, wherein the critical scale inhibitor is polyitaconic acid. <41 The limit school inhibitor is about O75-1 with the water.
2. A method according to claim 1, wherein the ingredients are mixed at a concentration of 0 ppm. (5) The method according to claim 4, wherein the water is seawater for desalination. (6) Seawater for desalination is mixed with a critical scale inhibitor consisting of polyitaconic acid or an alkali metal, ammonium or amine salt thereof having a weight average molecular weight of about 500 to 2000 at a concentration of about 0.5 to 10 ppm. Scale Y, consisting of adding to the seawater enough sulfuric acid to neutralize about 55-85% of the alkalinity due to its heavy carbon salts.
/ to stop drinking.